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GET /api/patches/2223548/?format=api
{ "id": 2223548, "url": "http://patchwork.ozlabs.org/api/patches/2223548/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pwm/patch/c5e7767cee821b5f6e00f95bd14a5e13015646fb.1776264104.git.u.kleine-koenig@baylibre.com/", "project": { "id": 38, "url": "http://patchwork.ozlabs.org/api/projects/38/?format=api", "name": "Linux PWM development", "link_name": "linux-pwm", "list_id": "linux-pwm.vger.kernel.org", "list_email": "linux-pwm@vger.kernel.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<c5e7767cee821b5f6e00f95bd14a5e13015646fb.1776264104.git.u.kleine-koenig@baylibre.com>", "list_archive_url": null, "date": "2026-04-15T14:50:12", "name": "[v1,1/2] pwm: stm32: Fix rounding issue for requests with inverted polarity", "commit_ref": null, "pull_url": null, "state": "accepted", "archived": false, "hash": "0cfb4f4d0fbe12f750d9bad839fd91039648649b", "submitter": { "id": 88686, "url": "http://patchwork.ozlabs.org/api/people/88686/?format=api", "name": "Uwe Kleine-König", "email": "u.kleine-koenig@baylibre.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-pwm/patch/c5e7767cee821b5f6e00f95bd14a5e13015646fb.1776264104.git.u.kleine-koenig@baylibre.com/mbox/", "series": [ { "id": 500001, "url": "http://patchwork.ozlabs.org/api/series/500001/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-pwm/list/?series=500001", "date": "2026-04-15T14:50:11", "name": "pwm: stm32: A rounding fix and a cleanup", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/500001/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2223548/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2223548/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linux-pwm+bounces-8590-incoming=patchwork.ozlabs.org@vger.kernel.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linux-pwm@vger.kernel.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=baylibre-com.20251104.gappssmtp.com\n header.i=@baylibre-com.20251104.gappssmtp.com header.a=rsa-sha256\n header.s=20251104 header.b=GxxFKP00;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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charset=UTF-8", "X-Developer-Signature": "v=1; a=openpgp-sha256; l=3091;\n i=u.kleine-koenig@baylibre.com; h=from:subject:message-id;\n bh=ajSHpn1BNzonBrH5M8RMYAzp3h9B89S9cIWnNvrv9aY=;\n b=owEBbQGS/pANAwAKAY+A+1h9Ev5OAcsmYgBp36Wn3t8V0cwMk6wJp4ND3V1gfyMohb6DSJJWf\n 9cMInW5qk+JATMEAAEKAB0WIQQ/gaxpOnoeWYmt/tOPgPtYfRL+TgUCad+lpwAKCRCPgPtYfRL+\n TnNvB/9+W/2Jab6L+30hO6T7u6hyyxLqJfIMDaAjeCbtPY+hhJtBlwYwdwTN0y48ovKKOB6MOpO\n O5U0WpFLZgrfzUQSxFT0Qzabf2FhdR1jacnbk8+dq2kQau/7hplscF/Uzw18UVDVfOXrUEgAkW2\n hax6KpmE81l0DGtEue+aODWW7iyUixYNQJMikXfZvc8tJ+XPotiIuPYqs5nR6+mRq5lbqZBNuPb\n t2SfQNVVfJ0DysXaNEjCOqyWzkHWboL/gJlRnCpiVJOHG0VuCFdLOAjSVSKJi6SS/LRncLflxVP\n nq+Whuh9IrMXT/HlXuDLLjB7as8f+w3U0wuqbHkiTaDI+ymi", "X-Developer-Key": "i=u.kleine-koenig@baylibre.com; a=openpgp;\n fpr=0D2511F322BFAB1C1580266BE2DCDD9132669BD6", "Content-Transfer-Encoding": "8bit" }, "content": "The calculation of the number of pwm clk ticks from a time length in\nnanoseconds involves a division and thus some rounding. That might\nresult in\n\n\tduty_ticks + offset_ticks < period_ticks\n\ndespite\n\n\tduty_length_ns + duty_offset_ns >= period_length_ns\n\n. The stm32 PWM cannot configure offset_ticks freely, it can only select\n0 or period_length_ns - duty_length_ns---that is the classic normal and\ninverted polarity. The decision to select the hardware polarity must be\ndone using the ticks values and not the nanoseconds times to adhere to\nthe rounding rules by the pwm core.\n\nWith the pwm clk running at 208900 kHz on my test machine\n(stm32mp135f-dk), a test case that was handled wrong is:\n\n\t# pwmround -P 9999962 -O 24970 -D 9974992\n\tperiod_length = 9999962\n\tduty_length = 9974840\n\tduty_offset = 25123\n\nWith this change applied the rounding is done correctly:\n\n\t# pwmround -P 9999962 -O 24970 -D 9974992\n\tperiod_length = 9999962\n\tduty_length = 9974840\n\tduty_offset = 0\n\nFixes: deaba9cff809 (\"pwm: stm32: Implementation of the waveform callbacks\")\nSigned-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>\n---\n drivers/pwm/pwm-stm32.c | 22 ++++++++++++----------\n 1 file changed, 12 insertions(+), 10 deletions(-)", "diff": "diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c\nindex 2594fb771b04..935257a890b0 100644\n--- a/drivers/pwm/pwm-stm32.c\n+++ b/drivers/pwm/pwm-stm32.c\n@@ -68,7 +68,7 @@ static int stm32_pwm_round_waveform_tohw(struct pwm_chip *chip,\n \tstruct stm32_pwm *priv = to_stm32_pwm_dev(chip);\n \tunsigned int ch = pwm->hwpwm;\n \tunsigned long rate;\n-\tu64 ccr, duty;\n+\tu64 duty_ticks, offset_ticks;\n \tint ret;\n \n \tif (wf->period_length_ns == 0) {\n@@ -164,23 +164,25 @@ static int stm32_pwm_round_waveform_tohw(struct pwm_chip *chip,\n \t\twfhw->arr = min_t(u64, arr, priv->max_arr) - 1;\n \t}\n \n-\tduty = mul_u64_u64_div_u64(wf->duty_length_ns, rate,\n-\t\t\t\t (u64)NSEC_PER_SEC * (wfhw->psc + 1));\n-\tduty = min_t(u64, duty, wfhw->arr + 1);\n+\tduty_ticks = mul_u64_u64_div_u64(wf->duty_length_ns, rate,\n+\t\t\t\t\t (u64)NSEC_PER_SEC * (wfhw->psc + 1));\n+\tduty_ticks = min_t(u64, duty_ticks, wfhw->arr + 1);\n \n-\tif (wf->duty_length_ns && wf->duty_offset_ns &&\n-\t wf->duty_length_ns + wf->duty_offset_ns >= wf->period_length_ns) {\n+\toffset_ticks = mul_u64_u64_div_u64(wf->duty_offset_ns, rate,\n+\t\t\t\t\t (u64)NSEC_PER_SEC * (wfhw->psc + 1));\n+\toffset_ticks = min_t(u64, offset_ticks, wfhw->arr + 1);\n+\n+\tif (duty_ticks && offset_ticks &&\n+\t duty_ticks + offset_ticks >= wfhw->arr + 1) {\n \t\twfhw->ccer |= TIM_CCER_CCxP(ch + 1);\n \t\tif (priv->have_complementary_output)\n \t\t\twfhw->ccer |= TIM_CCER_CCxNP(ch + 1);\n \n-\t\tccr = wfhw->arr + 1 - duty;\n+\t\twfhw->ccr = wfhw->arr + 1 - duty_ticks;\n \t} else {\n-\t\tccr = duty;\n+\t\twfhw->ccr = duty_ticks;\n \t}\n \n-\twfhw->ccr = min_t(u64, ccr, wfhw->arr + 1);\n-\n out:\n \tdev_dbg(&chip->dev, \"pwm#%u: %lld/%lld [+%lld] @%lu -> CCER: %08x, PSC: %08x, ARR: %08x, CCR: %08x\\n\",\n \t\tpwm->hwpwm, wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns,\n", "prefixes": [ "v1", "1/2" ] }